Though the Sandinistas already control all four branches of government and a majority of the municipalities, the former revolutionary party is equally concerned with controlling the streets, which they claim belong to them.

Since mid-2008 – just days after the Sandinista-controlled Supreme Electoral Council (CSE) banned two opposition minority parties from participating in last year's municipal elections – the Sandinistas have adopted a new zero-tolerance policy toward all opposition street-protests. In a July 5 speech Mr. Ortega famously warned that his Sandinista front will "raise the curtain of war" if the opposition tries to "overthrow what they call 'the dictatorship.' "

Since then, the Sandinista crackdown on street protests has been implemented with increasing vigor, especially following the accusations that the ruling party stole more than 40 mayoral seats in municipal elections last November. Opposition marches have been repeatedly attacked by Sandinista mobs – including masked men who are allegedly demobilized ex-gang members paid to join in the fray.

The Sandinistas tried to deter Saturday's protest marches in nine cities throughout the country by blocking the scheduled march routes. The protests led to bouts of violence in Managua and several other cities, as both sides threw rocks and shot homemade mortars at each other. Riot police – given explicit orders by Ortega "not to repress the people" – tried to keep the two groups separated.

Opposition lawmaker Luis Callejas was hospitalized with a serious head wound after reportedly being hit by a rock thrown by a Sandinista supporter in the northern city of Chinandega. He was among several injured in Saturday's clashes.

For Sergio Ramírez, one of Nicaragua's most internationally renowned intellectuals, the combination of electoral fraud and street repression is a formula for dictatorship, not revolutionary change.

"There are no democratic norms here. There's no right to vote, and no right to free mobilization," says Mr. Ramírez, who served as Ortega's vice president under the revolutionary government of the 1980s, and is now a fierce critic.

The Sandinistas, however, insist that controlling the streets is part of their revolutionary struggle.

Last month, Sandinista union leader and lawmaker Gustavo Porras called on all Sandinistas to assume permanent control of the streets, "because it is our natural form of struggle."

"With this struggle we have gotten where we are today, and we have to continue forward," Mr. Porras said.